High speed electrodeposition of nickel



United States Patent 3,488,264 HIGH SPEED ELECTRODEPOSITION 0F NICKELRaymond E. Bailey, Mentor, and Arthur H. DuRose, Richmond, Ohio,assignors to Kewanee Oil Company, Bryn Mawr, Pa., a corporation ofDelaware No Drawing. Continuation-impart of application Ser. No.443,077, Mar. 26, 1965. This application Sept. 27, 1968, Ser. No.763,409

Int. Cl. C23b 5/08, 5/46 US. Cl. 20449 9 Claims ABSTRACT OF THEDISCLOSURE A process for the high speed electrodeposition of nickelcomprising electrodepositing nickel on a cathode while employing aninsoluble anode from a chloride and bromide free bath consistingessentially of an aqueous solution of nickel ions having a pH within therange of 2.0 to 4.5 and containing a 1,2-benzopyrone compound, duringsaid electrodeposition said bath being rapidly passed over said cathodeat a current density of at least 500 amperes per square foot and at atemperature of at least 150 F.

This application is a continuation-in-part of application Ser. No.443,077 filed Mar. 26, 1965, now abandoned.

The present invention relates to high speed electrodeposition of nickel,cobalt, or nickel-cobalt alloys. More particularly, the inventionrelates to an improved process for such electrodeposition whereby smoothlustrous nickel, cobalt, or nickel-cobalt alloy is deposited on acathode at very high current densities and temperatures while avoiding abrittle deposit.

Theg reat majority of conventional processes for electrodepositingnickel, cobalt or nickel-cobalt alloy have refrained from utilizing highcurrent densities despite some practical advantages, such as fasterplating. Depending upon the composition of the plating bath, currentdensities of 200 amperes per square foot or higher have resulted inso-called burning; that is, the production of nickel hydrate at thecathode. Concentration polarization is associated with such high currentdensities under these conditions; and whatever the cause may be, thenickel deposit has been commercially unacceptable.

Attempts to utilize higher current densitites more satisfactorily haveincluded the use of plating baths operated at unusually hightemperatures, as well as baths which contain higher conductingsolutions. In particular, it has been suggested that the chloridecontent of the bath should be markedly increased or even that anallchloride bath should be employed to assist in the use of such highcurrent densitiessee High Speed Nickel Plating, Pinner & Kinnaman,Monthly Review, Amer. Electroplastics Assoc, 32, 22734 (1945). Suchbaths, particularly when operated at high temperatures, have not provedat all satisfactory. If insoluble anodes are used, chlorine is givenoff, and will, of course, attack the anode as Well as the platingequipment, and since it is a poisonous gas it must be removed from thearea. Furthermore, the nickel deposited from such a bath is exceedinglyfine grained and although it tends to be quite hard, it also tends to bequite brittle.

Attempts to utilize a very high current density with other types ofbaths, particularly all-sulfate baths, have overcome some of theseobjections but also have been 3,488,264 Patented Jan. 6, 1970unsatisfactory. An all-sulfate bath will produce a very coarse grainednickel deposit which tends to be more ductile than that deposited fromthe chloride-containing bath. But it has been very rough and notsufficiently ductile to be wholly satisfactory. In this connection, ithas been observed that for the all-sulfate bath, if the pH is increased,the ductility of the nickel deposit is decreased. Thus, it has beenconsidered necessary to use a low pH which, of course, presentsdifficulties.

Thus, no matter what general type of bath is employed, it is a mostdifficult problem to secure very high current densities underpracticable plating conditions and still maintain the bath properlywhile producing the desired properties in the nickel deposit. In fact,these results cannot be obtained without considerable agitation in thebath since it is necessary to provide a high rate of flow of theelectrolyte over the cathode surface. Theoretically, the limitingcurrent density for a sound nickel deposit increases with rate of flowof the electrolyte. There are, of course, many practical difliculties.In addition to some discussed above, these include the high voltageneeded, overheating of the electrolyte, the difliculties of anode tocathode spacing, and the problems caused by failure to maintain uniformflow of the electrolyte.

The electrodepositing of bright or semibright nickel under high currentdensities and high temperature conditions while at the same timeobtaining a deposit which is satisfactory as to ductility, smoothness,and adhesion presents a particularly difiicult problem. Addition agentsincorporated into a bath to provide a bright or semibright deposit, orto act as levelers; that is, to provide a smoother surface and to assistin hiding small imperfections in the basis metal, or both, are renderedmuch less effective, or in some cases completely ineffective, by theconditions of a high speed plating process. In fact, it has been statedby one authority, ClaussA Study of Variations in Certain Characteristicsof Bright Nickel Deposits With Variations in Bath Temperature, TechnicalProceedings, American Platers Society (1960), pp. -109, thisinvestigation of organic addition agents certainly shows thatsatisfactory bright nickel deposits may be obtained at high temperaturesbut the efiiciencies of existing useful compounds is decidedly low whencompared with the effectiveness at normal plating temperatures. Itshould be noted that this investigation did not utilize high currentdensities or high flow rates of the electrolyte; but the author noted,which has been our observation, that many common brighteners arerendered most ineffective or are completely destroyed by hot platingbaths, paticularly those depending upon unsaturation for theireffectiveness. The use of such addition agents is surely most desirableif bright or semibright nickel is to be obtained and they are mostdesirable in order to produce a grain structure of the desired type.They also should assist in producing a smooth surface; that is, theyshould provide some appreciable leveling effect or at least notinterfere with the leveling otherwise obtainable. Under the conditionsof the high speed plating process, it has not proved possible heretoforeto provide addition agents capable of gaining those desired resultsalthough some have aided in one way or another to some extent.

The addition agents contemplated by the present invention, contrary toexpectations, were found to enhance the brightening and leveling of thenickel deposit as compared with such efiects in a conventional nickelplating process despite the very high current densities andtemperatures, as well as the high flow rate of the electrolyte acrossthe cathode. In fact, in some instances, it has proved possible toproduce a fully bright nickel deposit from a bath by utilizing thesevery high current densities. Contrary to expectations, the desiredconcentration could be maintained readily in the bath without undueloss, while obtaining a deposit of satisfactory ductility andsmoothness.

Inasmuch as it is a necessary part of the present high speed platingprocess to obtain a high flow rate of the electrolyte, it is mostdesirable that contoured insoluble anodes be employed. Such anodes makeit easier to provide a uniform but minimum spacing between the anode andthe cathode so that more uniform current densities may be maintainedacross the cathode. While this result is always desirable, it isespecially important in the present process in view of the high currentdensities employed. In addition to the substantial saving in time, thisprocess also saves nickel since it has been shown that the recessedareas of the cathode or other parts of the cathode which would normallyhave a low current density, can be plated more readily. Thus, it is notnecessary to build up the thickness of the plate in high current densityareas to such a marked extent as is done in conventional processing.

Broadly, the instant invention comprises a high speed process for theelectrodeposition of nickel, cobalt, nickelcobalt alloy wherein themetal is deposited from a chloride and bromide free bath which employsinsoluble anodes. The bath is maintained at a pH in the range of 2.0 to4.5. Coumarin or a substituted coumarin is present as an addition agentin the bath. The bath of the instant invention is operated at atemperature of at least 150 F. utilizing current densities of at least500 amperes per sq. foot. The electroplating bath of the instantinvention must also be subjected to high agitation during plating withthe minimum agitation being a flow rate past the cathode of at least 300feet per minute. Each of the above mentioned essential aspects of theinstant invention will be discussed in detail in the remainder of thespecification.

In the practice of the present invention, the electroplating bathcomposition can be varied extensively so long as the bath is maintainedsubstantially free of chloride and bromide ions. Nickel salts such asnickel sulfate, fiuoborate, acetate, sulfamate, perchlorate, andtrichloroacetate may be used for supplying nickel to the solution.However, the all sulfate solution is preferred, and one substantiallyfree of chloride. Lead anodes can be used with the sulfate solution butnot when a substantial concentration of the other anions are present.During the electrolysis, nickel is deposited at the cathode and the pHdecreases. The solution may be regenerated by the addition of basicnickel compounds, such as nickel hydrate, carbonate, or oxide. It mayalso be regenerated by use of nickel powder or electrolytic means inauxiliary equipment. Also, semipermeable membranes have been used. Laterin the instant specification, a preferred embodiment will be discussedwith respect to pH which permits the most economical regeneration ofnickel baths useful in the instant invention.

During the practice of the instant invention, the temperature of theplating bath is maintained above 150 F., and preferably, although notnecessarily, within the range of 180 F. to 210 F. As the current isapplied, the plating solution is agitated very rapidly. This may beaccomplished by various well-known means, but preferably the agitationis carried out by pumping the electrolytic solution over the surface ofthe cathode at a rapid rate, which is at least 300 feet per minute andpreferably at least 600 feet per minute. When insoluble anodes areemployed, a very small spacing can be used between the anode and thecathode thus making this high flow rate easier to obtain. It isdesirable, however, that a substantially uniform flow rate be maintainedat the surface of the cathode, and due to turbulence, eddying, andother'fluid flow problems this may not be easily accomplished. It mayeven be necessary to place baffles at strategic points best learnedthrough experience.

As stated previously, the current density in the practice of the instantinvention must be greater than 500 amps per square foot. However, themaximum current density operable for a given plating operation isdirectly dependent on the rate of agitation or flow rate of the bathpast the cathode. For example, if the flow rate past the cathode ismaintained at 5 feet per second, the limiting current density in thepractice of the instant invention is about 700 amps per square foot. At22 feet per second the limiting current density is 3,000 amps per squarefoot whereas at a flow rate of 50 feet per second the limiting currentdensity is 8,000 amps per square foot.

The use of insoluble anodes such as lead, carbon, graphite, platinum,platinized titanium, and lead alloyed with small amounts of tin, silver,or cobalt is a necessary part of the present invention and results in aparticular advantage in the practice of the instant invention. Normally,insoluble anodes are never used in plating baths which contain organicadditives, the reason being that such organic addition agents arerapidly consumed by anodic oxidation. Surprisingly, however, in thepractice of the instant invention, it has been found that the anodicoxidation inherent in the use of insoluble anodes has a beneficialresult in the practice of the instant invention. The coumarin orsubstituted coumarin addition agents used in the instant inventiongradually breaks down at the cathode to form deleterious reductionproducts. However, these deleterious reduction products are controlledand maintained at a harmless level due to the anodic oxi dation effectedat the insoluble anode. The exact mechanism is not known with certaintybut it is known that melilotic acid is formed and its harmful effects onthe plating process are avoided whether it be by oxidation of theharmful acid at the anode which destroys side chains and gives off CO orwhether it polymerizes the melilotic acid so that the standard activatedcarbon treatment of such bath removes the same. Under ordinary platingconditions, the deleterious product formed at the cathode in bathscontaining a coumarin or derivative thereof will accumulate to aconcentration from about 0.025 M and begins to have harmful effects atabout 0.005 M. Under the high speed conditions of the instant inventionutilizing insoluble anodes in a substantially chloride free bath, thesedeleterious reduction products are destroyed at the anode and accumulateto a concentration of only about 0.001 to 0.002 M.

Coumarin may be used as a leveling and brightening agent under the abovedescribed high plating speed conditions which involve high temperatures,high agitation rates, insoluble anodes, and chloride free nickelsolutions. However, because of these conditions coumarin has a higherthan normal consumption rate. Because of the high temperature, thevolatilization of coumarin is higher than would be desired. Therefore,the use of leveling agents which have a lower electrolytic consumptionrate and/or volatilization rate would be advantageous. We have foundthat certain 1,2-benzopyrone compounds have these properties. Forexample, the volatility of 3-chlorocoumarin is not appreciably less thanthat for coumarin but the electrolytic consumption rate is about 25%less than that for coumarin. Methyl-coumarin has about the sameelectrolytic consumption rate as coumarin but a lower volatility.Acetylcournarin has both a lower electrolytic consumption rate and lowervolatility.

The substituent groups may be on either the aromatic ring or theheterocyclic ring of the coumarin molecule. The substituent groups maybe halogen, acetyl, hydroxy, hydroxymethyl, hydroxyethyl, methoxy,ethoxy, acetamino, N-formylamino, propargyl, cyano, methyl, ethyl,dirnethylamino, or diethylamino. Acidic substituents, such as carboxy,sulfonate, and sulfonamide groups are not Substituted 1,2-benzopyroneMoles per liter (1) B-chIorocoumarin (bromo, iodo, fluoro) 0. 0002-0.003 (2) 3-acetylcoumarin 0. 0002-0. 003 (3) dacetylaminocournarin 0.0002-0. 002 (4) 3-hydroxycoumarin 0. 0002-0. 002 (5) 3-cyanocoumarin 0.0002-0. 002 (6) 3- or 4-rnethyl coumarin 0. 0002-0. 003 (7) dmethylcoumarin 0. 0002-0. 003 (8) 4,8-dimethylooumarin 0. 0002-0. 003 (9)7-diethylamino-4-methyl 0. 0002-0. 002 (10) G-hydroxycoumarin 0.001-0.004 (11) 6(1-glucoseamino) couma 0. 0002-0. 002 (12)6-hydroxymethylcoumarin. 0.0002-0003 (13) S-hydroxyethylcoumarin 0.0002-0. 003 (14) 7-methoxycoumarin 0. 0002-0. 003 (15) B-ethoxycoumarin0. 0002-0. 003

In order that those skilled in the art may better understand how thepresent invention may be carried into effect, the following examples areprovided by way of illustration, but not of limitation. Unless otherwisespecifically indicated all temperatures are in degrees centigrade andall parts and percentages are by weight.

EXAMPLE I Two solutions containing 50 ounces per gallon of nickelsulfate and 6 ounces per gallon of boric acid were stirred uniformly ata temperature of 185 F. One solution contained 0.0004 mole per liter ofcoumarin and the other 0.0004 mole per liter of 3-chlorocoumarin, Thesolution surface area was 27 square inches. The loss of coumarin byvolatilization was 0.001 mole per liter per 1,000 hours and the loss of3-chlorocoumarin was 0.0008 mole per liter per 1,000 hours. When thesolution was electrolyzed at 1,000 amperes per square foot, theconsumption rate of chlorocoumarin was markedly less than that ofcoumarin, being at least 25 percent less.

Using the above solution but employing instead of 3- chlorocoumarin, thecompounds numbered 2, 3, and 8 of Table I, no measureable volatilizationloss of the addition agent was found.

EXAMPLE II A vinyl plastic sheet 12" x 16" was silvered by a commonreduction method and rinsed. It was then placed in a rectangularhorizontal cell and clamped into place so that it was one inch above alead anode of similar size. A solution containing 50 ounces per gallonof nickel sulfate, 6 ounces per gallon of boric acid, and 0.005 gram perliter of acetylaminocoumarin at about 150 F. was pumped through the cellat a speed of about 400 feet per minute. The pH of the solution was 3.5and was maintained at approximately this point by feeding nickelcarbonate into an auxiliary tank. Electrolysis was started at 100amperes per square foot for two minutes and then increased to 1,000amperes per square foot for nine minutes. The deposit was approximately7 mils in thickness and was semibright. However, it was burned in someareas.

The same experiment was conducted at 160 F. and 800 feet per minute, andin this instance the nickel deposit was considerably more ductile and noburning was observed.

Utilizing a set of conditions similar to that described in Example IIabove and utilizing a temperature of 160 F, and 500 feet per minute forthe rate of flow of the electrolyte; but employing 0.1 gram per liter of7-diethylamino-4-methyl coumarin as the addition agent, the deposit wasbright-semibright but slightly brittle. The addition of 0.1 gram perliter of trichloroethoxy ethanol made the deposit somewhat brighter andmore ductile.

EXAMPLE III One gallon of a Watts nickel solution containing 0.2 gramper liter of 3-chlorocoumarin was operated at F. and 600 amperes persquare foot for 600 ampere hours with 1%." rotating brass cylindricalcathode having a dimeter of 1%". An anode composed of nickel was soconfigured as to operate at an average current density of 50 amperes persquare foot. The addition agent was maintained at 02:0.1 gram per liter.At the end of this period, the build-up of the reduction products of theaddition agent (principally melilotic acid) had become 0.8 gram perliter. For this reason the nickel deposit was not fully semibright.

An experiment similar to that of Example In in an all sulfate bath wasperformed and a platinized titanium anode was used; that it, aninsoluble anode. As a result the breakdown products of the additionagent reached equilibrium at about 0.2 gram per liter and the depositwas fully semibright.

As stated earlier in the application, the plating bath of the instantinvention must be maintained in the pH range of about 2.0 to 4.5. In anplating bath employing the present invention, the bath should bebufiered so that the pH remains relatively constant during operation.When operating at pHs above approximately 3.0, it is beneficial to useboric acid to regulate the pH. The presence of the boric acid inaddition to affecting pH appears to have an effect on the ductility andbrightness of the deposit and is beneficial above a pH 3.0. At a pH of4.0 and above, boric acid is necessary to eliminate burning of thedeposit unless the agitation rate is extremely high.

The preferred pH range is between 2.5 and 3.2. Boric acid will notbuffer in this pH range and thus it is necessary to utilize an acidhaving a high buffer capacity in this pH range. Such buffers wouldinclude any acid having a pK value of between 2.0 and 4.85. Of course,these same buffering agents could be used at the other pH rangesoperable in the instant invention. The concentration of the bufferingagent used can vary from approximately 1 to 10 grams per liter dependingof course on the extent of use of the bath and the buffering capacitydesired. Typical buffers and their buffering concentrations are asfollows.

When operating in the preferred pH range or lower, an additionaladvantage is obtained by the practice of the instant invention. Whenoperating a chloride free nickel solution such as a nickel sulfate bathwith insoluble anodes, the pH drops and the nickel content of thesolution also decreases. It is therefore necessary to replenish thenickel and at the same time raise the pH to obtain uniform operatingconditions. The nickel supply can be replenished by the use of nickelhydrate, nickel oxide, nickel carbonate, nickel metal powder orelectrolytic means using anodes in an auxiliary tank. At a given pH thedissolution rate of nickel hydrate or commercial nickel carbonate isrelatively fast compared to nickel oxide or metal. However, the cost ofthe hydrate 7 and. carbonate is considerably higher than that of themetal or oxide.

It is therefore desirable to operate under conditions which will effectmore rapid dissolution of the metal or oxide. The higher the hydrogenion content (lower pH) the faster the metal or its oxide will dissolve.Therefore, by using the buffers of the instant invention, the pH of thesolution is maintained in the pH range wherein the metal and the oxidewill readily ionize and there is no need to use the more expansivenickel hydrate or nickel carbonate. Also the buffering agents tend tomaintain the pH at the same value and therefore permit easily obtaineduniform operating conditions.

To further illustrate the present invention, various examples are givenin the following tables using various buffering agents. The operatingconditions of the plating bath in the following examples consisted of 52oz. per gallon of nickel sulfate at a cathode current density of 1,000amperes per square foot and a temperature maintained at 180 F.

or a substituted coumarin compound in a concentration range ofapproximately 0.05 to about 0.5 gram per liter. The preferredconcentration of the coumarin compounds are between 0.1.and 0.3 gram perliter.

It has been stated earlier in the specification that in the lower pHrangebuffering agents having a pK value between 2.0 and 4.85 arepreferred and should also be pointed out that along with such bufferingagents boric acid may be added as a secondary buffer and in such casesthe concentration range of the boric acid can vary from preferably 1-3oz; per gallon.

We claim:

1. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodefrom a chlorine and bromine ion free bath consisting essentially of anaqueous solution of nickel sulfate having a pH within the range of 2.0to 4.5 and containing a 1,2-benzopyrne compound, during saidelectrodeposition said bath being passed at least 300 feet per minuteover said cathode at Addition Agents pH Ductility Appearance (1) N0buffer 2. 8-2. 4 Dull S.B. (2) N0 bufier 4. 0 Burned and exfoliated. (3)Boric acid 5 oz./gal 4. 0 5 Grey. (4) Boric acid 5 oz./gal 2. 8-2. 405-. 15 Dull S.B. (5) Boric acid 5 oz./gal. plus .2 g/l. coumar 2.5 5S.B. and leveling. (6) Na citrate 6.8 g./i 2. 5 5 Grey. (7) Na citrate6.8 g./l. plus .2 g./l coumarin. 2. 5 5 S.B. and leveling. (8) Nacitrate 6.8 g./l. plus .2 g./l. coumarin. 3. 8 06 Bt. With 81. burning.

2.5 .3 Dull S.B.

2. 5 5 S.B. and leveling. 3. 3 5 Bt. S.B. and leveling. 3. 8 04 Do. 3.85 Do. 2. 5 5 S.B. 2. 5 5 S.B. and leveling. 3. 8 08 Bt. S.B. withburning. (17) Acetic acid 2 cc./l 2. 5 4 S.B. (18) Acetic acid 2 cc./lplus .2 g./l. coumarin 2. 5 5 S.B. and leveling. (19) o-Phthalic acid 3g./l 2. 5 5 Grey. (20) o-Phthalic acid 3 g./l plus .2 g./l. coumarin 2.5 5 S.B. nd leveling. (21) o-Phthalic acid 3 g./l. plus 2 g./l.courmarin p 2. 5 5 Bt. S.B. leveling. (22) Boric acid 5 oz./gal. plus.25 g./l. butynediol. 2. 5 07 Bt. S.B. (23) n-Butyric acid 4 g./l 2. 5 5S.B. (24) n-Butyric acid 4 g./1. plus .2 g./l. coumarin 2. 5 5 S.B.- andleveling. (25) Formic acid 3 cc./l 2. 5 25 S.B. (26) Formic acid 3cc./1. plus .2 g./l. coumarin- 2. 5 5 S.B. and leveling. (27) Ni(BF4)z,4.0 g./l 2. 6 07 Bt. S.B. (28) Nl(BFa)2, 4.0 g./l. plus .2 g./l.coumarin 2. 6 5 Bt. S.B. and leveling. (29) KF'2H20, 2 g./l 2v 5 .3 Dull.B. (30) KF-2H2O, 2 g./l. plus .1 g./l. butynediol. 2. 5 25 S.B. withleveling. (31) KF-2H1O, 2 g./l. plus .1 g./l. butynediol plus 2 g 2. 5Bt. S.B. with leveling. (32) o-Phthalic acid 3 g./l 2. 5 5 Grey. (33)o-Phthalic acid 3 g./l. plus .2 g./l. oi fi-acetamide coumarin 2. 5 5S.B. with leveling.

In the ductility values given in the above table, the value .5 indicates.5 or better; S.B. indicates semi-bright; Bt. indicates bright and s1.indicates slight.

As can be noted from the examples given in the a v table in addition tothe presence of coumarin and a bulfering agent, certain unsaturatedcompounds may also be included in the plating bath and result inbrighter electroplate. Typical such unsaturated materials include bi(fl-hydroxyethoxy butyne-Z), diethyleneglycolmonopropargyl ether andbutynediol-1,4. These materials may be present in a concentration fromabout 0.005 to 0.5 gram per liter. The preferred concentration of thebutynediol is between about 0.2 and 0.3 gram per liter with a maximumutility appearing at a concentration of .25 gram per liter. Thebis-(B-hydroxyethoxy butyne-2) and diethyleneglycolmonopropargyl etherare present preferably in concentrations from 0.1 to 0.3 grams perliter. Maximum brightening appears when using bis-(B-hydroxyethoxybutyne-2) at a concentration of about 0.1 gram per liter while withdiethylene glycolmonopropargyl ether maximum brightening appears tocoincide with a concentration of 0.15 gram per liter. Such concentrationof these additional brightening agents may be added to the plating h fthe nstant invention which contains a coumarin a current density of atleast 500 amperes per square foot and at a temperature of at least F.,said compound having a boiling point greater than about 290 C. and amelting point greater than about 70 C.

2. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodefrom a chlorine and bromine ion free bath having a pH within the rangeof 2.0 to 4.5 consisting essentially of an aqueous solution of nickelsulfate and containing an addition agent selected from the groupconsisting of 3-chlorocoumarin, 3-acetylcoumarin, 6-acetylaminocoumarin,3-hydroxycoumarin, 3-cyanocoumarin, 3- or 4-mcthyl coumarin, 6- methylcoumarin, 4,8-dimethyl coumarin, 7-diethyl-amino- .4-n1ethyl coumarin,6-hydroxycoumarin, 6-(l-glucoseamino) coumarin, -6-hydroxymethylcoumarin, S-hydroxyethyl coumarin, 7-methoxycoumarin, andS-ethoxycoumarin, during said electrodeposition said bath being passedat least 300 feet per minute over said cathode, at a current density ofat least 500 amperes per square foot at a temperature of at least 150 F.

3. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodefrom a chlorine and bromine ion free bath having a pH Within the rangeof 2.0 to 4.5 consisting essentially of an aqueous solution of nickelsulfate and containing an addition agent selected from the groupconsisting of 0.0002 to 0.003 mole per liter of 3-chlorocoumarin, 0.0002to 0.003 mole per liter of 3-acetylcoumarin, 0.0002 to 0.002 mole perliter of 3-hylroxycoumarin, 0.0002 to 0.002 mole per liter of6-acetylaminocoumarin, 0.0002 to 0.002 mole per liter of3-cyanocoumarin, 0.0002 to 0.003 mole per liter of 3- or 4-methylcoumarin, 0.0002 to 0.003 mole per liter of 6-methyl coumarin, 0.0002 to0.003 mole per liter of 4,8-dimethyl coumarin, 0.0002 to 0.002 mole perliter of 7-diethylamino-4-methyl coumarin, 0.001 to 0.004 mole per literof 6-hydroxycoumarin, 0.0002 to 0.002 mole per liter of6-(1-glucoseamino) coumarin, 0,0002 to 0.003 mole per liter of6-hydroxymethyl coumarin, 0.0002 to 0.003 mole per liter of8-hydroxyethyl coumarin, 0.0002 to 0.003 mole per liter of7-methoxycoumarin, and 0.0002 to 0.003 mole per liter ofS-ethoxycoumarin, said bath being subject to high agitation so that thebath is rapidly passed over the surface of the cathode at a rateequivalent to at least 600 feet per minute, is supplied at a currentdensity of at least 500 amperes per square foot and a temperature of atleast 150 F.

4. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodefrom a chlorine and bromine ion free bath having a pH within the rangeof 2.0 to 4.5 consisting essentially of an aqueous solution of nickelsulfate and containing an addition agent selected from the groupconsisting of 0.0002 to 0.003 mole per liter of 3-chlorocoumarin, 0.0002to 0.003 mole per liter of 3-acetylcoumarin, 0.0002 to 0.002 mole perliter of 6-acetylcoumarin, 0.0002 to 0.002 mole per liter of 3-hydroxycoumarin, 0.0002 to 0.002 mole per liter of 3- cyanocournarin,0.0002 to 0.003 mole per liter of 3- or 4-methylcoumarin, 0.0002 to0.003 mole per liter of 6- methyl coumarin, 0.0002 to 0.003 mole perliter of 4,8- dimethyl coumarin, 0.0002 to 0.002 mole per liter of7-diethylamino-4-methyl coumarin, 0.001 to 0.004 mole per liter of6-hydroxycoumarin, 0.0002 to 0.002 mole per liter of 6-(l-glucoseamin0)coumarin, 0.0002 to 0.003 mole per liter of 6-hydroxymethyl coumarin,0.0002 to 0.003 mole per liter of 8-hydroxyethyl coumarin, 0.0002 to0.003 mole per liter of 7-methoxycoumarin, and 0.0002 to 0.003 mole perliter of 8-ethoxycoumarin, said bath being passed over the surface ofthe cathode at a rate of at least 600 feet per minute at a currentdensity in excess of 1,000 amperes per square foot and at a temperaturein the range of about 180 to 210 F.

5. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodefrom a chlorine and bromine ion free bath having a pH within the rangeof 2.0 to 4.5 consisting essentially of an acidic aqueous solution ofnickel sulfate and containing a 1,2-benzopyrone compound having aboiling point greater than 290 C. and a melting point greater than about70 C., said electrodeposition being further characterized in that thebath is subject to high agitation such that a flow rate at the cathodeof at least 300 feet per minute is produced and the current density atthe cathode is at least 500 amperes per square foot and the bathtemperature is at least 150 F.

6. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodefrom a chlorine and bromine ion free bath consisting essentially of abuffered aqueous solution of nickel ions having a pH within the range of2.0 and 4.5 and containing a 1,2-benzopyrone compound, said bufferingbeing produced by a buffer effective in the pH range of 2.0 to 4.0,during said electrodeposition said bath being passed over said cathodeat a rate of at least 300 feet per minute while employing a currentdensity of at least 500 amperes per square foot and operating said bathat a temperature of at least F.

7. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodeat current densities of at least 500 amperes per square foot at thecathode under high agitation conditions wherein the flow rate past thecathode is at least 300 feet per minute from a chlorine and bromine ionfree bath consisting essentially of an aqueous solution of nickel ionshaving a pH within the range of 2.5 to 3.2 and containing a1,2-benzopyrone compound along with a buffering agent capable ofbuffering said bath in the pH range of 2.5 to 4.0 which has a pK valuein the range of 2.0 to 4.85, said bath being maintained during saidelectrodeposition at a temperature of at least F.

8. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodeat current densities of at least 500 amperes per square foot at thecathode under high agitation conditions wherein the flow rate past thecathode is at least 300 feet per minute from a chlorine and bromine ionfree bath consisting essentially of an aqueous solution of nickel ionshaving a pH within the range of 2.5 to 3.2 and containing between about0.05 and 0.5 gram per liter of a 1,2-benzopyrone compound along withfrom 1 to 10 grams per liter of a buffering agent capable of bufferingsaid bath in the pH range of 2.5 to 4.0 which has a pK value in therange of 2.0 to 4.85, said bath being maintained during saidelectrodeposition at a temperature of at least 180 F.

9. A process for the high speed electrodeposition of nickel comprisingelectrodepositing nickel on a cathode while employing an insoluble anodeat current densities of at least 500 amperes per square foot at thecathode under high agitation conditions wherein the flow rate past thecathode is at least 300 feet per minute from a chlorine and bromine ionfree bath consisting essentially of an aqueous solution of nickel ionshaving a pH within the range of 2.5 to 3.2 and containing 0.1 to 0.3gram per liter of a 1,2-benzopyrone compound, 1 to 10 grams per liter ofa buffering agent capable of buffering said bath in the pH range of 2.5to 4.0 which has a pK value in the range of 2.0 to 4.85 and betweenabout 0.005 and 0.5 gram per liter of a compound selected from the groupconsisting of bis-(,B-hydroxyethoxy butyne-Z),diethyleneglycolmonopropargyl ether and butynediol, said bath beingmaintained during said electrodeposition at a temperature between 180 F.and 210 F.

References Cited UNITED STATES PATENTS 2,312,517 3/1943 Baker 204492,449,422 9/ 1948 Smith 20449 2,683,115 7/1954 Du Rose et a1 204492,694,041 11/1954 Brown 20449 2,782,152 2/1957 Du Rose et al 20449 OTHERREFERENCES W. A. Wesley et al.: 36th minual Proceedings of the AmericanElectroplaters Society, pp. 79-91 (1949).

A. G. Gray: Modern Electroplating, p. 307 (1953).

The Electrochemical Society, Modern Electroplating, p. 17 (1942).

JOHN H. MACK, Primary Examiner G. L. KAPLAN, Assistant Examiner UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,488 ,264January 6 1970 Raymond E. Bailey et al It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 7, line 10, "expansive same column 7, addition agent No. 21, acid3 g/l plus .2 g/l coumarin plus .25 g/l butynediol Column 9, line 15,0,0002" should read 0.0002 line 34, "6-acetylcoumarin" should read6-acetylaminocoumarin Signed and sealed this 10th day of November 1970.

" should read expensive should read o-Phthalic (SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, IR.

